In order to study the influences of grid scale on the wave breaking, three different computational grids are adopted in the simulation of the bow wave breaking of KCS at Fr=0.35. RANS approach coupled with high resolution VOF technique is used to resolve the free surface. It is found that when the ratio of the grid size to the hull length is about 1.5e-3, the breaking of bow wave can be better resolved. The sensitivity of bow wave breaking to the grid scale in x and y direction is the same as that in z direction.
The overturning and breaking of bow and shoulder waves, known as white water, is a complex phenomenon with many small-scale features, such as, air entrainment, capillary wave, which are always observed when the ship advances at high speed on the sea. The mechanism of bow wave breaking and its impact on ship hydrodynamic performance have not been well understood so it is of great significance to study the ship bow breaking waves. At present, the hydrodynamic experiment is the main way to study the ship bow wave breaking. In the formation of ship bow wave, the considerable vorticity originally at the toe was generated near the free surface. And the powerful counter-rotating vorticity concentrated near the wave crest was found by Dong et al. (1997). Being similar to the study of Dong, Roth et al. (1999) utilized particle image velocimetry to measure the flow structure and turbulence within the bow wave of DDG-51 model 5422. In the measurements, they also found that the negative vorticity originated at the toe of the wave while the positive vorticity was generated on the crest of the wave. In addition, they discovered that the great energy losses were experienced at the toe. Waniewski et al. (2002) studied the bow wave dynamics by using a deflecting plate, instead of a ship, in a supercritical flow in the flume experiments. In their study, the experimental data was compared with the results of Ogilvie (1972). The results demonstrated that the bow waves formed in the flume experiments with the depth equal to the draft was similar to the results obtained in towing tank experiments for the same Froude number. Duncan (1983) studied the breaking and nonbreaking wave resistance of a 2-D hydrofoil via the experiments in which he found the drag associated with breaking was more than 3 times the drag theoretically obtained with non-breaking waves.
